The reliability, durability, and functional integrity of electrical components can be inversely related to the operating temperatures experienced in such devices, whether the heat is generated by the device itself or from other sources. Semiconductor technology can be characterized as a quest to place more electronic components in less space to achieve greater speed and performance. As integrated circuits (IC's) and other semiconductor devices become faster, operating frequencies (e.g., clock speed in a microprocessor) also increase. At the same time, the distances between the conductive lines within the semiconductor device are reduced due to efforts to construct semiconductor devices that are increasingly compact. As the density of conductive lines and the clock speed of circuits increase, the amount of heat experienced in the device also increases. Therefore, it is critical to have an efficient heat removal system associated with IC's.
IC's can be formed on microelectronic dies and assembled into microelectronic packages by physically and/or electrically coupling the IC's to a package substrate. One or more microelectronic packages can be physically and/or electrically coupled to a printed circuit board (PCB) to form an “electronic assembly.” The electronic assembly can be part of an “electronic system.” An electronic system may be broadly defined herein as any product that includes an electronic assembly. Examples of electronic systems may include computers (e.g., desktop, laptop, hand-held, server, etc.), wireless communications devices (e.g., cellular phones, cordless phones, pagers, etc.), computer-related peripherals (e.g., printers, scanners, monitors, etc.), entertainment devices (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, MP3 (Motion Picture Experts Group, Audio Layer 3) players, etc.), and the like.
Specific areas of a die on which an IC is formed may be more frequently used than other areas of the die. For example, a floating point unit (FPU) area may generate a higher amount of heat than other areas on the die. The FPU areas lead to “hot spots” on the die that significantly increase the local temperature surrounding the hot spots, and also elevate the overall average temperature of the die.
One technique of conducting heat away from an IC chip may be by heat transfer to the PCB, and then to the case. The PCB may include features such as thermal vias and/or ground planes to further conduct the undesirable heat. Accordingly, “junction-to-board” thermal resistance is a factor in achieving efficient heat transfer to the PCB. The IC chip and the PCB may be spaced apart in an integrated semiconductor package assembly, such that the chip die and the PCB are not in direct contact. Thus, impediments to optimal junction-to-board heat transfer include substances interposed between the chip die surface and the PCB surface, such as air, or a substrate material in a wire bonding package (e.g., a stacked chip scale package (SCSP)), or an underfill material and/or solder bumps in a ball grid array (BGA) package assembly.